Determination of radon concentrations in household waters were performed in 1997 in three regions of south-western Poland which are considered to an have enhanced natural radioactivity level: in the Jelenia Gora and Walbrzych regions (both in south-western Sudety Mountains) and in the Upper Silesian Coal Basin, Water samples were collected from taps, wells and springs and were analyzed in a liquid scintillation counter. In the Upper Silesian Coal Basin all values are below 50 Bq/dm³ with a maximum of 32 Bq/dm³ and in the Sudety Mts. the radon concentration in water exceed this level in 68% of houses, reaching a maximum value of ca. 1400 Bq/dm³ in drilled well water in the Jelenia Gora region. The annual ingestion dose calculated for this value equals to ca. 0.5 mSv for infants, 0.4 mSv for children and 0.3 mSv for adults. The average annual effective whole body doses calculated for tap water samples for a representative population in the investigated regions range from about 0.02 mSv to 0.32 mSv and the maximum value reaches 1.39 mSv. The inhalation doses corresponding to the unit of water-borne radon concentration are about one order higher than the ingestion ones for tap water supplies.